1. Field of the Invention
The present invention relates to a blow-by gas ventilation system for an engine. More specifically, the present invention relates to a blow-by gas ventilation system particularly adapted for use in a small watercraft.
2. Description of the Related Art
In most four-cycle engines, including those utilized in personal watercraft, a portion of the fuel/air charge delivered to the combustion chamber passes beyond the piston ring(s) and into the crankcase chamber, before being combusted, due to the extreme pressures generated in the combustion chamber. These fuel/air gases, or “blow-by” gases, are generally reintroduced into the induction system of the engine, through a ventilation system, to be combusted along with a fresh fuel/air charge. The blow-by gases tend to collect oil mist generated by the movement of engine components within the crankcase, such as the crankshaft and connecting rods.
It is generally desirable to separate the oil mist component of the blow-by gases from the fuel/air component so as to avoid undesired combustion of lubrication oil. An oil separation system is typically employed to separate these components and route the majority of the oil portion back to the lubrication system and route the fuel/air portion into the induction system. However, in the context of a personal watercraft, it is often not practicable to provide a separate system within the limited space of the hull to perform this function, without detriment to the size and/or layout of other engine components.
Further, when an oil separation system is employed in an engine arrangement, the blow-by gases are typically introduced freely into a plenum chamber of the engine. With such an arrangement, any oil mist that was not successfully separated from the blow-by gases may come into contact with the air filter element within the plenum chamber. Over time, the oil mist may clog the air filter element and have a negative effect on performance due to reduced airflow through the air filter element.